Radical Alternating Copolymerization of Twisted 1,3-Butadienes with Maleic Anhydride as a New Approach for Degradable Thermosetting Resin

We report a novel approach for the synthesis of a readily curable and degradable resin by the radical alternating copolymerization of 1,3-diene monomers with maleic anhydride. 2,4-Dimethyl-1,3-pentadiene predominantly produced an alternating copolymer rather than a Diels-Alder adduct during the reaction with maleic anhydride. We revealed the most stable conformation as a twisted diene structure of 2,4-dimethyl-1,3-pentadiene and the other methyl-substituted dienes by DFT calculations, while a completely planar structure was preferred for the s-cis and s-trans conformers of the nonsubstituted butadiene. The highly alternating repeating structure of the produced copolymers was revealed based on the NMR analysis and copolymerization reactivity ratios. The alternating copolymers including an anhydride moiety and a carbon-to-carbon double bond in each repeating unit was conveniently used for the thermosetting, subsequent degradation, and polymer surface modification by postpolymerization reactions such as epoxy curing and oxidative ozonolysis.